Many compounds having a pyridonecarboxylic acid as a basic skeleton are known to be useful as synthetic antibacterial agents because they have excellent antibacterial activities and wide antibacterial spectra. Of these, norfloxacin (Japanese Patent Application Laid-Open No. 141286/1978), enoxacin (Japanese Patent Application Laid-Open No. 31042/1980), ofloxacin (Japanese Patent Application Laid-Open No. 46986/1982), ciprofloxacin (Japanese Patent Application Laid-Open No. 74667/1983), tosufloxacin (Japanese Patent Application Laid-Open No. 228479/1985) and the like are in wide clinical use as agents for treating infectious diseases.
However, these compounds have been not yet sufficient in antibacterial activity, intestinal absorbability, metabolic stability and side effects, particularly, phototoxicity, cytotoxicity, etc. Pyridone-carboxylic acid derivatives carrying cyclic amino group at the 7-position of the naphthyridine skeleton or quinoline skeleton have also been known (WO96/12704). However, It is still desired to develop compounds far excellent in absorbability and easy-to-synthesize.
It is therefore an object of the present invention to provide novel compounds satisfying all respects of antibacterial activity, oral absorbability, metabolic stability and side effects, particularly, phototoxicity, cytotoxicity, etc., and medicines containing such a compound.